Apparatus for detecting the presence of an occupant in a motor vehicle

ABSTRACT

A motor vehicle control system includes a pair of cameras for producing first and second images of a passenger area. A distance processor determines distances that a plurality of features in the first and second images are from the cameras based on the amount that each feature is shifted between the first and second images. An analyzer processed the distances and determine a size of an object on the seat. Additional analysis of the distance also may determine movement of the object and the rate of that movement. The distance information also can be used to recognize predefined patterns in the images and thus identify the object. A mechanism utilizes the determined object characteristics in controlling operation of a device, such as deployment of an air bag.

BACKGROUND OF THE INVENTION

The present invention relates to equipment for sensing the presence orabsence of objects, and more particularly to detecting whether anoccupant is present in a seat of a motor vehicle.

As a safety feature, modern motor vehicles incorporate air bags into thesteering wheel in front of the driver and into the dashboard in front ofa passenger in the forward seat. Additional air bags are being proposedfor the doors to the sides of these occupants. Rapid deceleration of themotor vehicle during an accident is detected and activates inflation ofthe air bags which the cushion the occupants.

Although air bags have greatly decreased the severity of injuries frommotor vehicle collisions, they occasionally cause injury to thepassenger or driver because of the rapid rate with which the air bagmust be deployed. In particular, the air bag may severely injure a smallchild or infant sitting in the front seat of the vehicle.

As a consequence, it is now recommended that small children and infantsride in the rear seat of the vehicle so as not to be exposed to theforce of air bag deployment in the event of an accident. However, thatdoes not address the situation which occurs when that recommendation isignored and a child rides in the front seat of the vehicle. Furthermore,in two passenger vehicles, such as sports cars and trucks, a child orinfant must be placed in a seat that faces an air bag. In this lattersituation, it has been proposed to provide a manual override switchwhich will disable the air bag in front of the child. However, not onlymust this switch be manually operated whenever a child is present, themotor vehicle operator must remember to re-activate the air bag foradult passengers.

These precautions also do not address the presence of a relatively smalladult occupant in a vehicle with an air bag designed to protect anlarger person. Thus there is a need to be able to customize air bagoperation in response to the size of an individual in the seat that isprotected.

However, in order to dynamically configure the air bag, its controlsystem must be able to reliably determine the occupant's size. Oneapproach that has been suggested is to sense the weight of the personsitting on the seat. However, weight alone does not indicate thekinematics of a person during a crash. For example, a person with a lowcenter of gravity and small upper torso will have dramatically differentkinematics as compared to a person with a small waist and muscular upperbody. That distinction in crash kinematics is very important indynamically configuring air bag operation.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a mechanism fordetecting the presence or absence of an occupant in a seat within amotor vehicle.

Another object is to implement that mechanism by means of a stereoscopicimage processing system.

A further object is to provide such a system with the capability ofdetermining the size of the seat occupant.

Yet another object of the present invention is to provide such a systemwith the capability of determining the sitting position of an occupant.

Another aspect of the present invention is to provide the stereoscopicimage processing system with the ability to detect motion in order todistinguish inanimate objects placed on the seat.

A further aspect of the present invention is to provide information forconfiguring the operation of an air bag in a motor vehicle to conform tothe physical characteristics of the seat occupant.

An additional aspect is to provide information about the occupant'skinematics in real time during a crash which would enable dynamicoptimization of air bag performance.

These and other objects are satisfied by a stereoscopic object detectionsystem which includes a pair of cameras that produce first and secondimages of the seat. Elements in the images are shifted in positionbetween the first and second images by an amount corresponding to adistance the elements are from the cameras. A distance processorcalculates the distances that a plurality of features in the first andsecond images are from the pair of cameras based on the shift of theposition of those feature between the first and second images. An imageanalyzer determines presence of an object on the seat from thedistances. The image analyzer also may determine the size of the objectfrom the distances

In the preferred embodiment of the stereoscopic object detection system,the distances are employed to detect movement of the object on the seatand the rate of that movement. Pattern recognition also can be performedon the distance information or on one of the first and second images tocategorize the object.

In one application of the present invention, the image analysis resultsare used by a mechanism to control operation of a device on the motorvehicle. For example those results may be employed to configuredeployment of an air bag in the motor vehicle to correspond to thephysical characteristics of a person on the seat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a motor vehicle incorporating an occupantdetection system according to the present invention;

FIG. 2 is a view from above the front seat of the motor vehicle;

FIG. 3 is a schematic block diagram of the present stereoscopic imageprocessing system to detect occupants in the motor vehicle seat;

FIGS. 4A and 4B form a flowchart of the method by which the fullstereoscopic images are processed;

FIG. 5 depicts the geometry of the triangulation method employed todetermine the distance between the cameras and an object in the vehicle;

FIG. 6 graphically depicts distance image data developed by thestereoscopic image processing system; and

FIG. 7 is a flowchart of the method by which predefined segments of thestereoscopic images are processed in real time.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2, the front portion of the passengercompartment of an automobile 10 includes a dashboard 12 from which asteering wheel 14 projects. A front seat 16 is spaced from the dashboard12 and includes a standard headrest 18 for both the passenger anddriver. As the driver also is a vehicle passenger in the broad sense,the term “passenger” as used herein shall refer to the driver as well asother occupants of the vehicle. The steering wheel has a centralcompartment which houses a first air bag 20 and the dashboard hasanother compartment which contains a second air bag 22 located in frontof the right portion of the seat 16.

Mounted above the windshield in the ceiling of the passenger compartmentis an assembly 24 of two separate video cameras 26 and 28 mountedside-by-side across the vehicle in the same plane. Each camera 26 and 28preferably is an imager in which each pixel location is randomlyaccessible, thereby enabling designated segments of their images to befed to an output without having to read out the remaining imageportions. Imagers of this type are referred to as an “active pixelsensor” (APS) and are described in U.S. Pat. No. 5,471,515, thedescription of which is incorporated herein by reference. Alternativelyother types of imagers, such as charged coupled devices (CCD), could beemployed with the sacrifice of the ability to randomly access imagesegments. Preferably the cameras 26 and 28 are responsive to nearinfra-red light and one or more sources 29 of infra-red light aremounted above the windshield to illuminate the front seat 16 of thevehicle. Such illumination allows operation of the present system atnight without affecting an occupant's ability to see the highway. Inaddition the illumination from source 29 fills in image shadows duringdaytime operation.

The left camera 28 has a horizontal viewing area indicated by the longdash lines in FIG. 2, whereas the right camera 26 has a horizontalviewing area indicated by the long and short dashed lines. The verticalviewing angles of each camera 26 and 28 are the same as indicated by thedashed lines in FIG. 1. The left and right cameras 26 and 28 produce afirst and second pair of stereoscopic images of the front seat 16 of themotor vehicle, as well as the body of occupant locations on that seat.Because the two cameras 26 and 28 are offset left to right across thevehicle, the first and second images, which are acquired substantiallysimultaneously, will contain essentially the same objects, but theobjects will be shifted horizontally between the two images. Thisproduces a stereoscopic pair of images which can be analyzed todetermine distances from the cameras to objects in the vehicle. As willbe described, that analysis employs well known photogrammetry techniquessuch as those used to measure height of geographic features in aerialphotographs. Alternatively, a single imaging device may be used with twosets of lens and mirror to focus a stereoscopic pair of images side-byside into the same imaging device. This alternative is considered to beequivalent to employing a separate camera for each stereoscopic image.

Although the left and right halves of the stereoscopic images areprocessed to determine the presence, positions and sizes of twopassengers on seat 16, for ease of explanation the processing of onlyhalf of the image will be described with the understanding that bothhalves are processed in the same manner.

With reference to FIG. 3, the images from the right and left cameras 26and 28 are applied to the inputs of an image processor 30. The imageprocessor 30 comprises a distance subprocessor 32 which determines thedistance that objects in the images are from the camera assembly 24, anda distance picture processing system 34 which analyzes the distancemeasurements to determine the presence, size and other characteristicsof an occupant on the motor vehicle seat 16.

The distance subprocessor 32 comprises a distance detector 36 whichlocates the same feature in each stereoscopic image and calculates thedistance to that feature. That distance measurement is stored withinmemory 38 as an element of a distance picture. The distance subprocessor32 is similar to one described in U.S. Pat. No. 5,530,420, thedescription of which is incorporated herein by reference.

The distance picture memory 38 is accessible by both the distancedetector 36 and by the distance picture processing system 34 via amemory interface 40. The memory interface 40 is connected to a set ofdata, address and control buses 42 which also connect to amicroprocessor 44. The microprocessor executes a program that is storedwithin a read-only memory 46 which analyzes the distance picture data,as will be described. A random access memory (RAM) 48 is connected tothe buses 42 to store intermediate results and other data utilized bythe microprocessor 44 during that analysis. The microprocessor 44 alsomay acquire a visual image directly from the right video camera 26 via acamera interface 49 connected to buses 42. An output memory 50 isprovided to hold the results of the distance picture analysis and aninterface circuit 52 communicates those results to devices outside thedistance picture processing system 34. In the case where the presentsystem governs the operation of an air bag within the motor vehicle, theinterface circuit 52 is connected to inputs of an air bag controller 54.That controller 54 also receives an indication from a collision sensor56 when an accident is occurring. The collision sensor 56 may provide anindication of the severity of the crash, e.g. rate of deceleration. Theair bag controller 54 responds to these inputs by activating the driverand passenger air bags 58.

The stereoscopic images are processed on a timed interrupt basis, forexample every ten seconds the entire stereoscopic image is analyzed,while only selected portions of the two images are processed everymillisecond. The full image processing commences at step 70 in the flowchart of FIG. 4A with periodic acquisition of the two stereoscopicimages from the right and left video cameras 26 and 28. At that time themicroprocessor 44 receives an interrupt signal and responds by issuing afull image acquisition command to the distance detector 36. Then at step72, the distance detector 36 analyzes the acquired stereoscopic imagesto find a small group of picture elements in one image that match agroup of picture elements in the other image, thus locating coincidingpoints on objects in each image. Such coinciding points may be objectfeatures such as edges, lines, and specific shapes.

The distance detector 36 upon locating the corresponding point in bothimages, utilizes photogrammetric triangulation in determining thedistance that such a point on an object in the images is the plane ofthe camera lens. That process is well known, see Paul R. Wolf inElements of Photogrammetry, 1974, McGraw-Hill, Inc. As shown in FIG. 5,the left and right cameras are spaced a distance r apart in the plane ofthe camera lens and each camera has focal points a distance f behind thecamera lens plane. Because of the left to right offset distance rbetween the two cameras, a discrepancy amount x will exist between thesame point in each camera image. Therefore the distance D between thecamera lens plane and the image point can be determined from theexpression: D=r(f/x). The values for r and f are known from the designof the camera assembly 24.

The discrepancy amount x between the right and left images is determinedat step 74 based on the difference in pixel locations of the coincidingpoint in the two images and the width of each pixel. By inserting thisvalue of x into the above expression, the distance detector 36 at step76 computes the distance value D which is stored in memory 38 at step 78as one of many elements of a distance picture. As will be described thedistance picture memory 38 is capable of storing two distance pictureswith data for a new set of stereoscopic images replacing the olderdistance picture. Thus the two most recently derived distance picturesalways will be retained in the memory 38.

Then, a determination is made at step 80 whether more coinciding pointshave to be located and processed in the stereoscopic images. When all ofthe coinciding image points have been processed, the distance picture isa two dimensional array of data with each location in the arraycontaining the distance for the correspondingly located point in thestereoscopic images. Thus, the data within the distance picture could beplotted graphically as a relief map of the image in terms of distancefrom the camera lens plane. An example of such a three dimensional plotis shown in FIG. 6 where x and y axes correspond to the pixel locationswithin the camera image and the z axis corresponds to the magnitude ofthe distance data for each pixel location. At the outer edges of thedistance picture, the data is relatively flat corresponding to thesurface of the seat 16, whereas the central portion of the imagecorresponds to an object which is placed on the seat. In point of fact,the distance values corresponding to the seat will be larger than thosecorresponding to the object as the vehicle seat 16 is farther from thecamera. Nevertheless, it should be noted that the edges of the objectare denoted by abrupt, large transitions in the distance data. Thisenables the outer boundaries of the object to be found. As will bedescribed, the volume of an object in the image can be derived bydetermining the average x and y dimensions between the object boundariesand the average distance valve.

Referring again to the flowchart of FIG. 4A, to analyze the distancepicture, the microprocessor 44 at step 82 scans the distance picture todetermine the difference between the data values corresponding to theseat 16 and the image portion which is closest to the camera. When thedifference between the distance to the seat 16 and the distance to otherimage features exceeds a threshold amount, the microprocessor 44concludes that an object is present on the seat 16. In order to avoiderroneous conclusions as may be produced by one or two spurious datapoints denoting a very close location to the camera, the microprocessormay require that there be a relatively significant number of points atwhich the distance exceeds that threshold in order to conclude that anobject is present on the seat 16. That determination is made at step 84in the image analysis and if true a flag is set in output memory 50. Ifit is concluded that a significant object is not present, the outputmemory 50 is cleared at step 83 and further analysis of the distanceimage terminates.

When the microprocessor 44 concludes that the data indicates a personmay be present, the distance picture is analyzed further at step 85 tofind the average distance between the camera and the person. The resultof that calculation is stored within the output memory 50. Next, at step86, the distance picture in memory 38 is analyzed to approximate thevolume of the person in the seat 16. In doing so, the microprocessor 44looks for the horizontal and vertical boundaries of the person which areindicated by relatively large transitions in the distance data as seenin FIG. 6. This provides a contour of the outer boundary of the personand standard techniques can be utilized to calculate the area withinthat boundary. Next the previously calculated average distance betweenthe seat 16 and the object is used as the third dimension of the personin the volume calculation. The result is stored in output memory 50.

At step 87 the left to right position of the person is found bydetermining the location of the volume with respect to the border of theimage. It is useful to know how close a passenger is to the door inorder to control the deployment of a side air bag. A further inspectioncan be made to determine the position of the volume with respect to thelower border of the image which indicates whether a large passenger hasslid down in the seat. The position information also is stored in outputmemory 50.

Then, at step 89, an analysis is performed on the distance picture tofind key physical features, such as the top of the person's head. Thiscan be determined by looking for a relatively large transition in thedata proceeding downward from the top of the distance picture. Thislocation of the top of the head indicates the relative height of thepassenger. The results of all these analyses at steps 85-88 are storedwithin the output memory 50 of the distance picture processing system34.

In many applications the image processing described thus far providessufficient information for controlling a device, such as an air bag, ona motor vehicle. However, the image data may be analyzed further toprovide additional information about the vehicle occupants. Subsequentprocessing can determine whether an object in the seat 16 is moving andthus distinguish between a large inanimate object and a person. To thisend, the analysis by distance picture processing system 34 progresses tostep 90 on FIG. 4B.

At this time the new distance picture in memory 38 is compared to theprevious distance picture which also is stored in that memory. If motionhas not occurred at one of the sitting positions in the vehicle seat 16during the ten second image acquisition period, then a determination canbe made that objects in the image are inanimate. This is accomplished atstep 92 by comparing the two distance pictures, data element by dataelement, and counting the number of pairs of data elements that differby more that a predefined amount. Alternatively, the two temporallydifferent video images from either the right or left camera 26 or 28 canbe compared to detect motion of an object. A slight variation isexpected between two distance images derived at different points intime, even when only inanimate objects are present, because of movementdue to vehicle vibration. Thus in determining motion, a negligiblechange in a given data point in the distance image will not beconsidered and a significant change of only a few data points also willbe ignored. However a significant change of a substantial number ofdistance data points indicates movement of the object on the vehicleseat 16. The exact amount of change between the value of a given datapoint and the number of data points which must have such a change inorder to be considered as indicating movement are functions of theresponse of the video cameras and the image resolution.

After comparing the two distance images, a determination is made at step94 whether substantial number M of data points have changed by therequisite amount. In that case a movement flag in the output memory 50is set at step 96 to indicate that the object at that sitting positionhas moved. Otherwise that movement flag is reset at step 98.

If desired, the image processing may continue by performing patternrecognition using any one of several well known pattern recognitiontechniques. For this purpose, the image processor 30 stores a reference,or master, pattern in random access memory 48. For example the referencepattern may be for an empty seat or an infant seat placed on the vehicleseat 16. The reference pattern is generated at step 100 by producing adistance picture of the reference stereoscopic images and processingthat distance picture to derive the pattern data. For example thedistance picture is processed to obtain object edge information whichthen is stored in random access memory 48 at step 103 by the programexecution branching there from step 102.

Thereafter during image processing at step 100, similar pattern data isderived from a new set of stereoscopic images. That pattern data iscompared at step 104 to the reference pattern. A determination is madeby the microprocessor 44 at step 106 whether there is a substantialcorrespondence between the new image pattern and the reference patternin which case an indicator flag is set in the output memory 50 at step106. Otherwise that pattern match flag is reset at step 110.Alternatively the visual images directly from the right camera 26 can beacquired via camera interface 49 and processed for pattern recognition.

Processing of the entire distance image then terminates at which pointthe output memory 50 of the image processor 30 contains the results ofthe various analyses performed. The air bag controller 54 is able toobtain those stored results via the interface circuit 52 and evaluatethe results in determining how to deploy the air bags 58 in the event ofan accident. The periodic, e.g., once every ten seconds, analysis of theentire stereoscopic image thus enables continuing update of theoperating parameters for the air bags. Such periodic review of theoccupancy situation of the seat accounts for changes in the sittingposition and other movement of the individual within the vehicle cabin.

When the image processor 30 results indicate that a person was notpresent within the seat 16, the air bag need not be deployed as suchwould serve no purpose. Furthermore, if the analysis by microprocessor44 indicates that a person occupying the vehicle seat 16 has arelatively small volume and/or was relatively short as determined by thelocation of the top of that person's head, it is likely that the seatoccupant is a child. In those cases, the air bag controller 54 woulddisable deployment of the air bag.

In a situation where the microprocessor 44 concluded that a sufficientlylarge person is present, the initial rate at which the air bag isinflated during an accident would be set to correspond to the occupant'svolume, height and average distance to the air bag. Specifically, thecloser the person is to the air bag and the larger the person, thefaster the rate of deployment.

During the crash the kinematic information about the person's movementis useful to regulate the rate of air bag inflation to correspond to theseverity of the accident. The faster the crash and the greater theforces acting on the occupant, the faster an air bag should inflate. Thepresent image processing system also can provide kinematic informationabout the occupant without additional hardware.

Therefore, present system processes selected segments of thestereoscopic images more frequently, than processing the entire images,to provide real time information as to how the occupant is moving duringa crash. To this purpose, the microprocessor 44 also executes ainterrupt routine depicted in FIG. 7 every millisecond, for example.This interrupt routine commences at step 120 with the microprocessor 44sending a command to the distance subprocessor 32 via memory interface40 which instructs the distance detector 36 to acquire and process apredefined portion of the stereoscopic images from video cameras 26 and28. The predefined portion of each image may comprise two segments often columns of picture elements within each image which correspond tothe center of the normal sitting positions for the seat occupants. Thesesegments then are processed to determine parameters for controlling theair bag associated with those two sitting positions. For simplicity onlythe processing of the image segments for one of those sitting positionswill be described.

The distance detector 36 at step 122 locates coinciding points orfeatures in the image segments from each camera in the same manner aswas performed with respect to the entire image described previously.Then the discrepancy amount x between the coinciding points in thestereoscopic image segments is determined at step 124 and used at step126 to calculate distance data for the image segment. That distance datais stored in a section of the distance picture memory 38 at step 128.The distance picture memory 38 has two sections of additional storagelocates in which distance data for image segments are stored. Onesection stores data for the most recent set of image segments and theother section contains previous image segment distance data with eachnew group of data overwriting the memory section containing the oldestdistance data.

The microprocessor 44 in the distance picture processing system 34 thentakes over by computing the change in distance between the two storedsets of distance data at step 130. The change information is stored inthe output memory 50 at step 132. Because the distance data is acquiredat regular intervals, e.g. every millisecond, the changes corresponddirectly to a rate of change in distance or in other words the speed atwhich the object on the seat is moving. The speed can be calculated andstored in the output memory 50 or the air bag controller 54 may simplyuse the distance change data directly. In either case this data in theoutput memory corresponds to the object speed.

The speed related data is made available to the air bag controller 54via the interface circuit 52. The air bag controller 54 regulates therate at which the air bags 58 inflate in response to the speed at whicha vehicle occupant is approaching the respective air bag during anaccident.

What is claimed is:
 1. A stereoscopic object detection system forsensing and categorizing objects present on a seat of a motor vehicle,the stereoscopic object detection system comprising: a camera assemblyfor producing first and second images of the seat in which imagefeatures are shifted between the first and second images by an amountcorresponding to distances the image features are from the cameraassembly; an image analyzer coupled to the camera assembly andprocessing the first and second images to determine presence of anobject on the seat, and to determine a size of the object in response toa given amount that the object is shifted between the first and secondimages; and an output device coupled to the image analyzer and producinga signal in an event that the presence of an object on the seat isdetected, wherein the signal indicates the size of the object on theseat.
 2. The stereoscopic object detection system as recited in claim 1wherein the camera assembly comprise an image sensor in which segmentsof the first and second images are randomly accessible.
 3. Thestereoscopic object detection system as recited in claim 1 furthercomprising a processor connected to the camera assembly and whichdetermines distances that a plurality of features in the first andsecond images are disposed from the camera assembly, wherein thedistances are determined in response to a given amount that theplurality of features are shifted between the first and second images.4. The stereoscopic object detection system as recited in claim 3wherein the image analyzer employs the distances in determining thepresence of an object on the seat.
 5. The stereoscopic object detectionsystem as recited in claim 3 wherein the image analyzer employs thedistances in determining the size of the object on the seat.
 6. Thestereoscopic object detection system as recited in claim 1 furthercomprising a image analyzer which employs information from the cameraassembly to detect movement of an object on the seat.
 7. Thestereoscopic object detection system as recited in claim 1 furthercomprising a pattern detector which receives information from the cameraassembly and processes the information to recognize presence of apredefined pattern in at least one of the first and second images. 8.The stereoscopic object detection system as recited in claim 7 whereinthe pattern detector comprises a memory for storing a reference pattern;and a processor which detects presence of the reference pattern in theinformation from the camera assembly.
 9. The stereoscopic objectdetection system as recited in claim 7 wherein the reference pattern isfor a child seat.
 10. The stereoscopic object detection system asrecited in claim 8 wherein the reference pattern denotes a physicalcharacteristic of a motor vehicle operator.
 11. The stereoscopic objectdetection system as recited in claim 1 further comprising a mechanismconnected to the output device and controlling deployment of an air bagin response to the signal.
 12. The stereoscopic object detection systemas recited in claim 7 the camera assembly comprises a pair of cameras.13. A stereoscopic object detection system for sensing and categorizingobjects present on a seat of a motor vehicle, the stereoscopic objectdetection system comprising: a camera assembly for producing first andsecond images of the seat and objects thereon, in which image featuresare shifted between the first and second images by an amountcorresponding to distances the image features are disposed from thecamera assembly; a distance processor connected to the camera assemblyfor determining distances that a plurality of features in the first andsecond images are from the camera assembly, wherein the distances aredetermined in response to a given amount that each feature is shiftedbetween the first and second images; an analyzer coupled to the distanceprocessor to analyze the distances and determine a size of an object onthe seat; and a mechanism for controlling operation of a device of themotor vehicle in response to the analyzer.
 14. The stereoscopic objectdetection system as recited in claim 13 further comprising anotheranalyzer employs the distances in determining whether an object ispresent on the seat.
 15. The stereoscopic object detection system asrecited in claim 13 further comprising another analyzer which employsthe distances in detecting movement of the object.
 16. The stereoscopicobject detection system as recited in claim 13 further comprisinganother analyzer which employs the distances in detecting a rate ofmovement of the object.
 17. The stereoscopic object detection system asrecited in claim 13 further comprising a pattern detector whichprocesses information from the camera assembly to recognize presence ofa predefined pattern in at least one of the first and second images. 18.The stereoscopic object detection system as recited in claim 13 whereinthe mechanism controls deployment of an air bag.
 19. A method forcontrolling operation of an air bag in an vehicle, said methodcomprising step of: acquiring an image of a passenger area of thevehicle; processing the image to determine a size of a person in thepassenger area; processing the image to detect movement of the person inthe passenger area; and controlling operation of the air bag in responseto the size of the person in the passenger area and in response towhether movement of the person is detected.
 20. The method as recited inclaim 19 wherein processing the image to detect movement producesinformation regarding a rate of movement of the person in the passengerarea; and the step of controlling operation of the air bag is further inresponse to the rate of movement.
 21. The stereoscopic object detectionsystem as recited in claim 1 wherein the camera assembly has a singleimaging device which produces the first and second imagesstereoscopically side-by-side.
 22. The stereoscopic object detectionsystem as recited in claim 11 wherein the mechanism controls a rate atwhich the air bag is deployed.
 23. The stereoscopic object detectionsystem as recited in claim 13 wherein the camera assembly has a singleimaging device which produces the first and second imagesstereoscopically side-by-side.
 24. The stereoscopic object detectionsystem as recited in claim 18 wherein the mechanism controls a rate atwhich the air bag is deployed.
 25. The method as recited in claim 19wherein controlling operation of the air bag controls a rate at whichthe air bag is deployed.
 26. A system for controlling operation of anair bag in a motor vehicle, which system comprises: a camera having animaging device which stereoscopically produces first and second imagesside-by-side wherein image features are shifted between the first andsecond images by an amount corresponding to distances the image featuresare from the camera; an image analyzer coupled to the camera andprocessing the first and second images to determine presence of a personin the motor vehicle and to determine a size of the person in responseto a given amount that the person is shifted between the first andsecond images; and a mechanism for controlling operation of the air bagin response to the size of the person.
 27. The system as recited inclaim 26 wherein the image analyzer derives a volume measurement of atleast a portion of the person; and the mechanism controls operation ofthe air bag in response to that volume measurement.
 28. The system asrecited in claim 26 wherein the image analyzer determines a distancethat the person is from the camera, and the mechanism controls operationof the air bag in response to that distance.
 29. The system as recitedin claim 26 wherein the image analyzer produces kinematic informationabout the person; and the mechanism controls operation of the air bag inresponse to the kinematic information.
 30. The system as recited inclaim 26 wherein the image analyzer produces information regarding arate of movement of the person; and the controls operation of the airbag in response to that rate of movement.